Setting up an SSH server on Ubuntu is about as simple as it gets. The server of choice is OpenSSH.
Run this command from a terminal window:
sudo apt-get install ssh
To test that it’s working, you can try to ssh into your own machine:
> ssh localhost
The authenticity of host ‘localhost (127.0.0.1)’ can’t be established.
RSA key fingerprint is 98:8a:b8:b2:9e:8a:84:e0:d4:08:27:fb:74:f0:de:d4.
Are you sure you want to continue connecting (yes/no)?
Looks like it’s working! Naturally our ssh client doesn’t have the key for the server, since we just installed it. You can type yes to continue or just hit Ctrl-C to stop.